1. Field of the Invention
The present invention relates to a tape automated bonding tape, hereinafter referred to as "TAB tape" and a method for producing the same.
2. Description of the Related Art
A TAB tape known in the art comprises a base film having an electrical insulating property and a conductor pattern formed on the base film. Such a TAB tape is characterized in that it can provide an extremely fine conductor pattern.
For producing a TAB tape, its conductor pattern is made by forming such conductor film as copper foil and the like on base film and then by etching the conductor film in the shape of a required pattern. Since the conductor film is supported on the base film of the TAB tape, it becomes possible to use a conductor film which is much thinner than a conventional metal lead frame and to form a conductor pattern of high-density which cannot be formed by such a conventional metal lead frame.
Because the base film of the TAB tape supports the conductor pattern as mentioned above, this base film itself must have an electrical insulating property. In addition, this base film must have a certain heat-resisting property, since the TAB tape is hermetically sealed with resin after a semiconductor chip is mounted on thereon. Therefore, a heat-resisting plastic film such as polyimide film or the like is used as the base film.
However, such a known TAB tape has the following problems that; the plastic film such as polyimide film or the like used as the base film is relatively expensive material; the base film has moisture-absorbency and this causes cracks in the sealed resin after being hermetically sealed with resin; the adhesiveness between the base film and the sealed resin is not always satisfactory; because of the softness and low rigidity of the base film, the conductor pattern is subject to be deformed; the deformations of the sprocket holes formed in the base film cause insufficient positioning accuracy; and the difference between the coefficient of thermal expansion of the conductor pattern and that of the base film causes warps in the attached condition between the base film and the conductor pattern.